Today I learned...

[shinta|hikari]

Did you just notice how many changes you were proposing to the Japanese language just to validate your point?

Using Romaji will make things difficult due to homonyms, not to mention the alphabet is English, not Japanese. They can't use pure hiragana and katakana because Japanese text has no spaces between words.

Exclusive Romaji and Hiragana/Katakana text is also going to be much longer because they simply take more space.

Kanji is also used in typed text, so penmanship affects only a small facet of it.

You simply cannot compare losing cursive to losing kanji. Cursive is being lost due to a lack of practicality, while Kanji is being kept because of practicality. Cursive is a writing style, while Kanji is an integral part of the Japanese language.